Europe's nationalists include far-right parties that are now in coalition governments, such as Mr Salvini's League and Austria's Freedom Party.

But nationalist themes have also been increasingly adopted by more traditional centre-right parties, such as Germany's CSU, Britain's Conservatives and Austria's People's party.

Politicians such as the UK's Nigel Farage have capitalised on complaints that the EU grabbed too many of the traditional powers of the nation and controls everything from national budget deficits to citizenship rights.
Marlene Awaad

The nationalists' dominant issue is usually immigration — and the need to defend the nation against "swarms" of migrants from outside the west. When it comes to economics, they are often drawn to Trump-style protectionism.

These nationalists are also hostile to international institutions and treaties, which they regard as the playthings of a rootless, global elite.

The Trump administration has withdrawn from international treaties such as the Paris climate accord, and organisations like the UN Human Rights Council. The European nationalists focus their ire on the EU and the international rules governing the treatment of refugees.

Increasingly, they are looking to co-operate. Sebastian Kurz, Austria's chancellor, has mused about organising a "Berlin-Rome-Vienna" axis to fight illegal immigration.

Richard Grenell, the US ambassador in Germany, has talked about empowering Trump-style "conservatives" across Europe.

Steve Bannon, Mr Trump's former chief strategist, convened meetings of nationalist parties in Rome during the Italian elections, writing later: "It's hard not to feel we're on the right side of history."

Beyond the West

The nationalists are often fans of Vladimir Putin. The Russian president is admired as a tough guy who sticks up for his nation.

His violation of international laws in the process is regarded as a plus — not a minus. By contrast, the nationalists detest Angela Merkel, the German chancellor, and Justin Trudeau, the Canadian prime minister, who are seen as preachy internationalists, hopelessly soft-headed on the defining issue of immigration.

This nationalism is not confined to the west.

In Delhi, recently, I had a long conversation with Jayant Sinha, a government minister. He argued that the Modi government rejects universalism, in favour of a defence of India's unique culture.

"People feel their heritage is under siege," he said, "in that sense we are part of a global narrative."

Many liberal internationalists find it hard to accept that the nationalists are making progress partly because they have some genuine political insights.

Their emphasis on the enduring importance of the nation-state clearly resonates with voters. Demands for tougher control of illegal migration flow naturally from that idea — since the question of who is entitled to citizenship is central to national identity.

Europe's nationalists, such as Mr Salvini, Mr Orban and Britain's Nigel Farage, have capitalised on complaints that the EU grabbed too many of the traditional powers of the nation and controls everything from national budget deficits to citizenship rights.

The central demands of the new nationalists, such as control of immigration or protectionism, have a legitimate place in democratic politics. But the policies adopted by them, once they are in power, have quickly spun off into horrifying directions, such as the detention of migrant children in the US or Mr Salvini's demand for a mass expulsion of the Roma population from Italy.

One key problem is that the nationalist emphasis on the nation-state usually has a strong cultural and racial element. Once you start thinking of outsiders as less worthy than your compatriots — indeed, as people who "infest" your nation (in the words of President Trump) — than it becomes much easier to treat them brutally.

A second problem is that the new nationalists often ignore the complexity of the modern world. International rules are not simply the product of the ideological preferences of an unmoored globalist elite. They are the necessary means to regulate the interactions of nations on everything from trade to travel. Abolish all those fussy international laws and you are on the route to anarchy, a trade war — or a real war.

So while the nationalists are making common cause in taking on their liberal internationalist foes around the world, the "nationalist international" is intrinsically unstable. A world in which nation-states see each other above all as rivals is one that is primed for conflict. gideon.rachman@ft.com